Preparation And Application Of Hydrophobically Modified Alginate Electrospun Nanofibers

Sodium alginate (SA) electro-spinning nanofibers have excellent high moisture absorption, biocompatibility, biodegradability, high porosity, and large surface area, lightweight and other characteristics. However, current research on SA nanofibers is less, mainly because the rigidity extending molecular chains of SA make the chain entanglements of SA insufficient in an aqueous solution, using static electricity spinning technique to prepare pure SA nanofibers is very difficult. Amphiphilic copolymer prepared by hydrophobic modification of SA usually appears microphase separation to form a certain micro areas. Meanwhile, modified SA destroys the intramolecular hydrogen bonds, molecular chain flexibility increases, and is expected to blend with polyvinyl alcohol (PVA) and form a tighter chain entanglement, to prepare electro-spinning nanofibers with more uniform morphology and better drug loading and release properties.This study mainly used potassium persulfate (KPS) as initiator, used diacetone acrylamide (DAA) to hydrophobically modify sodium alginate (SA), prepared amphiphilic copolymer sodium alginate-poly diacetone acrylamide (SA-PDAA). The structure and performance of SA-PDAA were characterized by infrared spectroscopy (IR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), gel filtration chromatography (GFC), fluorescence analysis, element analysis and X-ray diffraction (XRD). IR test results showed that SA-PDAA was synthesized successfully; DSC and TGA tests showed that the hydrophobic long chain on main chain of SA affects the thermal properties of the original SA; the hydrophobic long chain makes the main chain of original SA bend, and has a certain hydrophobic property. Element analysis showed that with the increase of DAA addition amount, the grafting ratio of SA-PDAA was higher, and the grafting ratio of SA-PDAA1.0was41.17%. GPC analysis showed that during the reaction process, SA appeared certain degradation, and the molecular weights of SA-PDAA were all less than the raw material SA, and with the increase of grafting ratio, the molecular weight of SA-PDAA increased. XRD tests showed, SA was a kind of amorphous high-molecular polymer, the grafted hydrophobic long chain changed the crystal structure of the original SA, with the increase of the grafting ratio, characteristic diffraction peaks of PDAA and XRD were stronger, characteristic peaks corresponding to SA at2θ=21.8°moved to the lower angle direction in SA-PDAA, and with the increase of grafting ratio, the crystal space increased gradually. Fluorescence analysis revealed that SA-PDAA had certain amphipathy and surface-activity, the surface tension of SA-PDAA solution decreased compared to the SA solution, and with the increase of grafting ratio, the critical aggregation concentration (CAC) was smaller, the CAC gradually reduced from2.452g/L to0.072g/L.The study also prepared spinning liquid by compounding SA-PDAA with PVA, and conducted electros-pinning under different process parameter conditions respectively, to find the optimum conditions for electro-spinning. The optimum spinning process of SA-PDAA/PVA electros-pinning nano fibers was that the ambient temperature was25℃, relative humidity was40%, voltage was20KV, a flow rate was0.4mL/h, receiving distance was20cm. It manifested as a more uniform fiber, smaller diameter and the smallest diameter distribution.Simultaneously, the study still investigated the effects of SA-PDAA and SA-PDAA/PVA(V/V) with different grafting ratios under different proportions on the viscosity, surface tension, and conductivity of SA-PDAA/PVA spinning solution under optimum conditions. And the morphology of electro-spinning nanofibers was observed under different spinning solution by scanning electron microscopy (SEM). Experimental results show that when compounding SA-PDAA and PVA with different grafting ratio respectively according to the same volume ratio, the viscosity, surface tension and conductivity of the spinning solution also showed the same trend, decreased with the increase of SA-PDAA grafting ratio. When volume ratio was the same, the viscosity increased and the surface tension and conductivity decreased with the increase of PVA volume fraction. By observing and analyzing SEM images of electro-spinning nanofibers, when the ratio of SA-PDAA/PVA (V/V) spinning solution that compounded SA-PDAA1.0with a grafting ratio of41.17%and PVA was20:80, the fiber morphology was the best.In this study, the broad-spectrum new insecticide acetamiprid was taken as a model drug to test the drug release performance of SA-PDAA/PVA electro-spinning nanofibers. Experimental results showed that the morphology of nanofibers was not uniform after loaded with drugs; drug release performance results showed that SA-PDAA/PVA drug-loaded nanofibers had a significant effect of drug delivery; Peppas model equation was used to analyze the drug release mechanism of drug-loaded fiber within24h, SA-PDAA/PVA electro-spinning nanofibers drug release mechanism belonged to Non-Fickian diffusion model.Through the above experimental analysis and deduction, modified SA molecular chains were grafted with hydrophobic long chains, destroyed the hydrogen bond within the SA molecular chains, the hydrophilic fraction of the molecular chains reduced, rotation steric hindrance of the intramolecular chains reduced, the flexibility improved, the intramolecular chains rotated and curled and improve the chain entanglement. After adding PVA, strong hydrogen bond effect was formed between PVA and SA-PDAA molecular chains, SA-PDAA molecular chains further bended and tangled together with PVA flexible molecular chains, which made SA-PDAA more spinnabile. Meanwhile, hydrophobic association effect of SA-PDAA and auxiliary and crosslinking effect of PVA in fibers made the blend network more stable, the drug could be packaged inside the fiber more uniformly. Right because of the entanglement among the SA-PDAA molecular chains, the SA-PDAA could effectively resist the external force during the stretching process of electro-spinning, was not prone to breakage, and was conducive to the electro-spinning process.